Action Points

Note that this study was published as an abstract and presented at a conference. These data and conclusions should be considered to be preliminary until published in a peer-reviewed journal.

Note that this randomized trial demonstrated that anti-HIV antibodies were superior to placebo in delaying HIV rebound among virally-suppressed individuals who discontinued therapy.

Be aware that larger studies will be needed to determine whether such a treatment approach could supplant ART in some patients.

PARIS -- Infusions of anti-HIV antibodies delayed the resurgence of the virus after standard triple-drug therapy was stopped, a researcher said here.

The delay, compared with that experienced by patients given a placebo, was modest but statistically significant, according to Trevor Crowell, MD, of the U.S. Military HIV Research Program in Bethesda, Md.

The study, conducted in Thailand among patients whose HIV was diagnosed and treated early, used a bNAb called VRC01, which is among the first to be tested in humans. The goal of the so-called RV397 trial was to see if infusions of the antibody could delay HIV rebound once treatment was stopped.

It did so, Crowell reported.

Patients getting the placebo saw their virus rebound to more than 1,000 copies of HIV RNA per milliliter of plasma -- a preset endpoint -- within a median of 14 days. In contrast, patients getting the antibody saw rebound after a median of 33 days, a difference that was significant.

One participant, however, had control of the virus for 42 weeks before rebounding just days before this week's presentation, Crowell reported.

Broadly neutralizing antibodies play a key role in defense against many pathogens, but only about 20% of people with HIV make such molecules naturally and it usually takes them two or three years, commented Anthony Fauci, MD, director of the National Institute of Allergy and Infectious Diseases.

"The somewhat comforting news," Fauci told reporters, is that scientists have learned to make bNAbs in the lab, using B cells from people with HIV, and more than 200 are now available to study.

Some of those -- such as VRC01 -- have been put into forms approved for administration to people and are under study in clinical trials.

In principle, Fauci said, bNAbs could have three uses:

Passively transfer to people at risk of HIV to prevent infection

Treat people with, for instance, a strain of HIV resistant to antiretroviral drugs

Allow people to stop taking antiretroviral drugs

The RV397 study is an early cut at the last goal, but researchers have also mounted two large trials, also using VRC01, to test the first.

The so-called AMP trials -- for Antibody Mediated Protection -- will enroll 1,500 young women in Africa and 2,400 men who have sex with men in North and South America, according to Myron Cohen, MD, of the University of North Carolina Chapel Hill.

In those trials, participants will get 10 infusions, either of placebo or one of two concentrations of the antibody, Cohen said. He noted that -- unlike drug trials where there is usually some prior evidence of efficacy -- there's no idea if the antibodies will work.

But he said organizers have been "taken aback by the enthusiasm" of volunteers who are putting trial accrual well ahead of what had been expected. Currently, he said, some 1,493 men and 923 women have signed up, about 20% more than had been anticipated.

So far, he said, investigators have safely delivered some 6,500 infusions and 90% of the volunteers have stayed in the study.

That's a good sign, commented Linda-Gail Bekker, MBChB, PhD, of the Desmond Tutu HIV Centre in Cape Town, South Africa. "There really was some skepticism that people would step up for intravenous infusion," said Bekker, who is also president of the IAS.

If early trials show some success, Fauci said, the next steps are to use more powerful antibodies, test them in combination, see if they can be delivered subcutaneously rather intravenously, and try to find versions that are long-lasting.

The antibody research will also play into the search for an HIV vaccine, Cohen said. If a bNAb or some combination of bNAbs can be shown to have a preventive benefit, scientists could likely develop a vaccine that elicited such antibodies.

The study had support from the Henry M. Jackson Foundation for the Advancement of Military Medicine and the U.S. Department of Defense. Crowell and Jintanat are employed by the U.S. Military HIV Research Program.

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